Restoration of threatened plant species in Limahuli Valley on the Hawaiian Island of Kaua'i in the framework of the Global Tree Assessment

Abstract

Societal Impact StatementTrees are an important part of many ecosystems. The Global Tree Assessment data can be used to focus conservation and restoration efforts for the circa 30% of tree species that are threatened worldwide. The conservation status for the tree flora of Limahuli Valley on Kaua'i Island and a restoration plan for 11 endangered tree species is evaluated in the Global Tree Assessment framework. Lessons learned from Limahuli Valley, one of the most biodiverse valleys in the Hawaiian Islands, provide recommendations for developing long‐term sustainable restoration projects.Summary Based on conservation status assessments of the world's circa 60,000 trees, the Global Tree Assessment (GTA) report revealed that 30% (17,500) of known tree species are currently at risk of extinction. This study aims to evaluate the conservation status for the tree flora of Limahuli Valley and a restoration plan for 11 endangered tree species, in the Global Tree Assessment framework. Of the 117 tree taxa found in Limahuli Valley, 83 (71%) have been assessed for the International Union for the Conservation of Nature (IUCN) Red List and 90% of the assessed tree taxa are threatened. However, only 19 (21%) of these are federally listed and nine tree taxa were not found under their current name or at all in the GlobalTree Portal, suggesting a need for additional curation as well as a conservation status assessment gap. Progress has been made in Limahuli Valley on most restoration goals suggested by the GTA framework, but challenges remain related to both access to material for restoration, mitigation of threats, and understanding correlates of survivorship. Furthermore, trees only constitute about 40% of the flora in Limahuli Valley, and it is important to also consider nontrees including ferns and allies to strive for restoration of an ecosystem as well as the targeted species.